The present invention relates to a cleaning apparatus for a photoconductor which is installed in an electrophotographic copier or the like and, more particularly, to a cleaning apparatus which efficiently removes and collects residual toner particles from a photoconductor by using magnetic brushes which are formed by magnetic carrier particles.
In an electrophotographic copier of the type which develops a latent image electrostatically formed on a photoconductor, or a recording medium, part of the toner usually remains on the photoconductor surface even after the toner image has been transferred to a sheet. To remove the residual toner particles and thereby clean the photoconductor surface, the copier is furnished with a cleaning apparatus which includes a magnetic brush device for forming magnetic brushes and removing the toner particles thereby, and a toner collector device for collecting the removed toner particles. A prior art magnetic brush device comprises a non-magnetic sleeve which has permanent magnets thereinside for holding magnetic brushes and is supplied with a voltage of a polarity opposite to that of the toner particles in order to adsorb the toner particles. Meanwhile, a prior art toner collector device comprises a toner collector sleeve supplied with a voltage higher than the voltage applied to the non-magnetic sleeve, thereby adsorbing the toner particles out of the magnetic brushes in the magnetic brush device. The toner particles deposited on the toner collector sleeve are usually scraped off the sleeve by a blade or the like which is held in pressing contact with the periphery of the sleeve, a suitable receptacle being employed for collecting the shaved toner particles.
A problem encountered with such a prior art cleaning apparatus is that the toner particles adsorbed by the brushes on the non-magnetic sleeve cannot be shifted to or efficiently adsorbed by the toner collector sleeve unless a voltage higher than the voltage applied to the non-magnetic sleeve is applied to the toner collector sleeve. The extremely high voltage thus applied to the toner collector sleeve is disadvantageous because it allows the voltage to leak from the toner collector sleeve to the non-magnetic sleeve across the magnetic brushes formed by the magnetic carrier particles, the leak greatly effecting the operation for toner collection.